Guides
AUX, Bluetooth or USB: Which Way to Connect a Phone to Car Audio Is Most Reliable?
AUX is the most predictable path, Bluetooth the most convenient, and USB only works when the head unit accepts digital audio. A comparison of signal path, latency, power and compatibility, plus the checks that solve noise and silence in a car.
One Headphone Channel Silent or Quieter? The Check Order from Plug to Cable to DAC
A dead channel usually comes from a contact or the cable. Uneven volume is more often driver tolerance, ear tip seal or a channel balance setting. Six checks in order of cost, plus a symptom table and the point where repair is the only option.
Bluetooth Transmitter vs Receiver: What's the Difference, and How Do You Add Bluetooth to Old Gear? (with KEYSION S1 and S2)
A Bluetooth transmitter sends TV, CD or computer audio out; a receiver brings phone audio into an old amp. Use the wiring, power and codec tables to work out which one your setup is missing.
What Is Headphone Resolution, and How Do You Tell How Much Detail a System Really Retrieves? (With KEYSION 02 Pro and 16G/24G Cables)
Resolution is not bright treble. It is how well a system recovers quiet notes, decay tails and layering at low distortion and low noise. This guide gives measurable thresholds, a five-minute listening test, and an honest look at what cables and DACs can and cannot change.
How Do You Connect a Wired DAC to an iPhone? Lightning vs USB-C Adapters, Explained (with KEYSION 01, 02 and the OTG Cable)
iPhones have had no headphone jack since the 7, so a wired DAC has to go through a port. There are two paths: iPhone 14 and earlier need Apple's camera adapter, while iPhone 15 and later take a USB-C DAC directly. This article covers what each generation requires, where the Lightning power ceiling sits, why Apple Music's hi-res lossless needs an external DAC, and why a dual Type-C OTG cable simply cannot serve a Lightning iPhone.
How Do You Care For and Store Headphones So They Last? Moisture, Cable Coiling and Eartip Replacement (with KEYSION 30A and Storage Cases)
Hard eartips, a channel that cuts out, a muffled tone: those usually are not a broken headphone. They come from three small things adding up, moisture inside the housing, a cable bent at the same point, and tips aged by skin oil. This piece gives replacement windows for tips, pads and cables, plus a washing, coiling and dry-storage routine, and says which kind of case suits which situation.
Can You Use a USB DAC With PS5 or Switch? Console USB Audio Limits, Explained (with the KEYSION 02 Pro and 01)
A dongle DAC that stays silent on a PS5 or Switch is usually hitting the console USB audio bar: UAC1 only, 48kHz ceiling. We cover the per-console requirements, mode switching and cable choice.
Headset Mic Not Working? CTIA vs OMTP Wiring: What Differs and How to Tell (with the KEYSION Mic01)
A silent headset mic is usually a wiring mismatch, not a fault. We break down the CTIA and OMTP pin order, how to test which one your headset uses, and when an adapter is the right fix.
What Is Bluetooth Multipoint? How One Headset Connects to a Phone and a PC at Once (with the KEYSION S2 and 01)
Multipoint keeps one headset online with two devices at once and switches to whichever is playing. This guide separates multipoint from device memory, explains the sound and latency costs, and gives a checklist when the switch misbehaves.
IEMs or Over-Ear Headphones: How Do You Choose Between the Two? (with the KEYSION 02 Pro and 30A Eartips)
IEMs trade a tight seal for isolation and bass; over-ears trade size for soundstage and a gentler fit. This guide compares isolation, soundstage, comfort and drive difficulty, then gives a three-step way to choose.
Line Out vs Headphone Out: What Is the Difference, and Can You Plug Headphones Into a Line Out? (with the KEYSION 02 Pro)
A line out sends a fixed-level signal with no headphone amp; a headphone out is amplified and adjustable. Here is how they differ, what happens when you plug headphones into a line out, and how to wire a KEYSION 02 Pro or S2.
Why Does Volume Jump Between Tracks? Loudness Normalization and ReplayGain Explained (with the KEYSION 02 Pro)
Volume that jumps from track to track usually comes from mastering loudness, not a broken device. Here is how loudness normalization and ReplayGain differ, what platforms target, and how to set it up on an external DAC.